[RL] R3 Fix the bug for determining the end of a request

[gongshaotian]

Motivation

Fix the bug of failing to promptly determine the end of a request：

• Only one EOS token was decoded
• After obtaining Block, model runner immediately launched EOS tokens
• When the maximum length is exceeded, replace the last token with an EOS token

NOTE：R3 does not support the pooling model

TODO: Unable to promptly determine the end of the request

• Cherry-pick to develop branch

Modifications

ModelRunner：

• Use the generation of EOS tokens as the condition for determining the end of the request
• Implemented in post-process

Usage or Command

None

Accuracy Tests

None

Checklist

• Add at least a tag in the PR title.
  • Tag list: [[FDConfig],[APIServer],[Engine], [Scheduler], [PD Disaggregation], [Executor], [Graph Optimization], [Speculative Decoding], [RL], [Models], [Quantization], [Loader], [OP], [KVCache], [DataProcessor], [BugFix], [Docs], [CI], [Optimization], [Feature], [Benchmark], [Others], [XPU], [HPU], [GCU], [DCU], [Iluvatar], [Metax]]
  • You can add new tags based on the PR content, but the semantics must be clear.
• Format your code, run pre-commit before commit.
• Add unit tests. Please write the reason in this PR if no unit tests.
• Provide accuracy results.
• If the current PR is submitting to the release branch, make sure the PR has been submitted to the develop branch, then cherry-pick it to the release branch with the [Cherry-Pick] PR tag.

[paddle-bot]

Thanks for your contribution!

[codecov-commenter]

Codecov Report

❌ Patch coverage is 8.00000% with 23 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release/2.4@603aab0). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
fastdeploy/model_executor/pre_and_post_process.py	10.00%	16 Missing and 2 partials ⚠️
fastdeploy/config.py	0.00%	1 Missing and 1 partial ⚠️
...model_executor/layers/moe/routing_indices_cache.py	0.00%	2 Missing ⚠️
fastdeploy/worker/gpu_model_runner.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff               @@
##             release/2.4    #6388   +/-   ##
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  Coverage               ?   56.22%           
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  Files                  ?      333           
  Lines                  ?    42248           
  Branches               ?     6427           
==============================================
  Hits                   ?    23756           
  Misses                 ?    16634           
  Partials               ?     1858           

Flag	Coverage Δ
GPU	56.22% <8.00%> (?)

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[gongshaotian]

magic number?